Page 1 METIS First Master Training & Seminar Localization-Based Systems (LBS) Al Akhawayn University...

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METIS First Master Training & Seminar

Localization-Based Systems (LBS)

Al Akhawayn University in Ifrane

Professor Driss Kettani

Ahmed Eloufiremail: (D.Kettani/Ah.Eloufir)@aui.ma

Page 2 METIS First Master Training & Seminar, Ifrane (Morocco), 15-16.03.2007

The METIS project is managed by the European GNSS Supervisory Authority through Euro-MED GNSS I project

1. Introduction2. LBS and GIS3. Components of LBS4. Context of use of LBS5. What are LBS used for?6. Architectural aspects7. Categories of LBS8. Overview of most known LBS systems9. Applications

Localization-Based Systems (LBS): Plan of the Presentation


1. Introduction

It is an information System whose main value is related to the processing/exploitation of the spatial position of its data… Device independent…

LBS allow to define the location of a point situated on the surface of Earth…

The need of a Projection system… UTM, Lambert Planar, Albers Conic Equal Area, etc.

The SADD effect… Shape, Area, Distance, Direction distortion due the projection system…

The link between the physical feature on earth and its “spatial coordinates” is not always accurate…

The use of the appropriate projection system impacts directly the accuracy of the LBS added value…


3D sphericalcoordinates areprojected onto theprojection surface(a map sheet) to create a flat planar coordinate system.

Most Distorted

Most Distorted

Least Distorted

1. Introduction


2. LBS and GIS

LBS allows to locate an object on the earth surface, whereas GIS allows to describe the location of the object.

Having a coordinate location is, generally, of little value: i.e. knowing that object A is located in (-6.85,34) would make a little sence, however, if we say that object A is located in the intersection of “Boulevarde de France” and street “Oued Oum Rabii” in Rabat, Agdal, would definitely make more sence.

LBS allows mapping in GIS:

Collect points coordinates (x,y) with LBS...

Calibrate image map using those points and LBS coordinate system...

Create features on the new calibrated map...


Most of the time: LBS = Location/Communication infrastructure + GIS + user device…

3. Components of an LBS


4. Context of use of an LBS


5. What are LBS used for?

Location: determining a basic position. Example…

Navigation: getting from one location to another . Example…

Tracking: monitoring the movement of people and things. Example…

Mapping: creating maps of the world. Example…


6. General Architecture (1/2)


6. General Architecture (2/2)

Satellite Constellation

Ground Stations

GPS Receiver

Mobile Phone (GSM)

Sign

al Signal

L

B

S

GIS

Coordinate System


7. Categories of LBS: 7.1. Satellite-based localization

Generally, they are composed of:

Space segment: a constellation of satellites…

Control Segment: The monitoring stations continually monitor satellite positions and provide updated times and ephemeris for the satellites to keep them in synchronism with standards of time and position on the Earth…

User Segment: Receivers…

A receiver obtains signals from the satellites so as to calculate its coordinates





If you know you are 10 miles from satellite A in the sky, you could be anywhere on the surface of a huge, imaginary sphere with a 10-mile radius.

If you also know you are 15 miles from satellite B, you can overlap the first sphere with another, larger sphere. The spheres intersect in a perfect circle.

If you know the distance to a third satellite, you get a third sphere, which intersects with this circle at two points.


7. Categories of LBS: 7.2. GSM-based localization

GSM Network: System Architecture

GSM Network: Geographical Structure


7. Categories of LBS: 7.2. GSM-based localization

Positioning with GSM:

Cell of Origin (COO)

Timing Advance (TA)

Time of Arrival (TOA)

Time Difference of Arrival (TDOA)

Angle of Arrival (AOA)


7.2.1. Positioning with GSM: COO

The method uses the cell area in which the mobile station is registered by identifying the cell-ID of serving cell, BTS can be found.

The BTS has a fix position and known properties, such as signal strength

An area around the BTS can be calculated in which the handset should be located to receive signals in this cell.

This method is fairly inaccurate. The area calculated around the BTS is based on transmitted signal strength and known signal attenuation, which would give a radius around the BTS.

This method depends upon the network cell size, which can vary from 150m in an urban area up to 35,000m in a rural area.


7.2.2. Positioning with GSM: TA

A way to improve COO is to enhance the method using the Timing Advance value, (TA).

TA is used to synchronize the signals between the MS and the BTS.

Each increment of the TA value corresponds to a distance of about 550m (e.g. TA value of 0 means the MS is between 0 and 550m away from the BTS, a value of 5 means between 2750 and 3300m away).

By using the TA value, in addition to the COO, the circle around the BTS will be narrowed down to an approximate 550m wide arc.

The TA value is stored in both the network and the MS, and can be retrieved at both positions.


7.2.3. Positioning with GSM: TOA

TOA works by measuring signals sent from the MS to three or more BTSs.

By sending a known signal the BTS can receive the signal and hand it over to a Location Measurement Unit (LMU).

The LMU measures the time it took for the signal to travel between the MS and the BTS, the TOA value.

These values can be used to calculate a circle around the BTS, since the propagation time of the radio wave is directly proportional to its traversed distance. Calculating where the circles from three different BTSs intersect will give the proximate location of the MS (Triangulation).


7.2.4. Positioning with GSM: TDOA

TDOA is a variation of the TOA, and can be used if the time the signal was sent isn’t known or not accurate.

The LMU at the BTS marks the time when the signal arrived from the MS, d1.

This value is compared against when the signal arrived to another BTS, d2.

The difference between the two arrival times, d1-d2, is called the TDOA value.

A curve is calculated along the line where the TDOA value is constant, a hyperbola.

By using two pairs of BTSs, at least three BTSs, two hyperbolas can be calculated and an intersection found where the MS is located.


7.2.5. Positioning with GSM: AOA

If the angle in which the signal from the MS arrives to the BTS can be measured, a line can be drawn from the BTS using this angle…

By measuring the angle at two or more different BTSs an intersection of the lines can be calculated where the MS would be located…

An advantage of this method is that only two BTSs are required to find an intersection…

The main disadvantage is the need of complex antennas to measure the angle…


7. Categories of LBS: 7.3. Other types of localizations

Wireless signal positioning…

TV signal positioning…

IP address positioning…

Domain name system (DNS) positioning…


8. Overview of most known LBS systems: 8.1. Global Positioning System (GPS)

Name: NavStar Global Positioning System (GPS) Owner: US Department of Defense Dates:

Launching :1973 Operational: 1978

Cost: 13M$ Characteristics:

24 satellites 6 orbits (55°) Altitude: 20180km Revolution: 11h58min

Frequencies: 1575.42 MHz civilian 1227.60 MHz military


8. Overview of most known LBS systems: 8.2. Galileo

Name: Galileo Owner: ESA (European Space Agency) Dates:


Cost: 3.6M€ Characteristics:

30 satellites 3 orbits (56°) Altitude: 23222km

Frequencies:

1164-1215 MHz 1215-1300 MHz 1559-1592 MHz


8. Overview of most known LBS systems: 8.3. GLONASS

Name: Global Navigation Satellite System (GLONASS) Owner: USSR Dates:


Cost: N/A Characteristics:

24 satellites 3 orbits (64.8°) Altitude: 19130km Revolution 11h15min40s

Frequencies: 1602.94-1614.94 MHz civilian 12240-1260 MHz military


9. Applications: 9.1. e-Tourism

Remote Tourist Tracking (RTT): The RTT is a tool that allows tracking, monitoring and helping tourists exploring harsh regions.

It requires tourist vehicles to be

equipped with spatial localization devices (a GPS receiver) and connected, thanks to a wireless communication media (e.g. GSM), to a Central Tourist Server. The RTT is based on a tracking system that localizes in real time groups of tourists around the region.


9. Applications: 9.2. e-Transport

E-Transport allows companies to manage their fleet

in an effective/optimized way… Back office and front office… E-Transport includes three components:

A tracking and guidance component… An intelligent delivery schedule and planning

component… A driving follow up component…


9. Applications: 9.2. e-Transport Architecture


9. Applications: 9.3. Geo-GSM

Geo-GSM: The objective of the Geo-GSM tool is to provide

proximity information services to GSM users using SMS/MMS

messages and without any specific localization device…

Typical queries that the Geo-GSM can handle are:

What is the nearest Café?

What is the phone numbers of the hotels that are in proximity?

What is the address of the nearest Pizzeria?

How far is the train Station?


9. Applications: 9.3. Geo-GSM Architecture


Thank You!

http://www.aui.ma/GNSS/metis/

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